Background: The restless legs syndrome (RLS) is a movement disorder characterized by an imperative urge to move the legs, associated with paraesthesias, motor restlessness and worsening of symptoms at night with at least partial relief by activity. Its prevalence ranges between 2-15% of general adult population and 20-30% of uremic patients. Aim: To evaluate the frecuency and the clinical features of RLS in a sample of general adult population and in uremic patients, in Chile, correlating it with biochemical parameters. Method: 100 relatives of outpatients and 166 uremic patients undergoing chronic haemodialysis were interviewed assessing the presence and severity of RLS according to current diagnostic criteria. Biochemical parameters assessed were hematocrit, serum ferritin, phosphate, intact parathyroid hormone (iPTH) levels. Results: 13% of the general population sample was affected, 15% of them were severe. Forty three cases were found among uremic patients (25.9%) (p <0.01 vs general population), 60% of them were severe and women were affected with higher frequency (p <0.05) and severity (p <0.01). Four patients presented RLS even during hemodialysis. No correlation was found with biochemical parameters. Most RLS cases had not been diagnosed previously. Conclusions: In our population RLS is common and undetected. It is especially prevalent and severe in uremic patients: we found no evidence that anaemia, iron deficiency or iPTH level play a major pathogenic role. Our findings emphasize the need of greater medical awareness of RLS because available therapy may improve the quality of life (Rev Méd Chile 2001; 129: 179-86).